Artificial leather manufacture



Jan. 30, 1934. O, WQODRUFF 1,945,173

ARTIFICIAL LEATHER MANUFACTURE Filed July 27, 1932 pasted Jan. 30,1934 1,945,l73

UNITED STATES PATENT OFFICE i 1,945,173 ARTIFICIAL LEATHER MANUFACTURE Frank 0. Woodrufi, Newton, Mass., assignor, by

mesne assignments, to Beckwith Manufacturing Company, Boston, Mass, a corporation of Massachusetts Application July 27, 1932. Serial No. 625,032 13 Claims. (01. 92-41) This invention relates to the manufacture of formed into the web, I prefer to add a solution artificial leather ,throughthe use of suitable of the coagulant, as by spraying, to the wet, fibrous material and aqueous rubber dispersions freshly-formed web immediately before it reof the nature of latex as raw materials. ceives the latex and is then plied. Indeed, even In making artificial leather from latex and a when a coagulant is added to the stock, I prefer 60 web of fibers, such as formed on a papermaking to spray coagulant solution onto the web, then or carding machine, it is difiicult to accomplish to apply the latex, and finally again to spray a satisfactory distribution of rubber as-a binder coagulant solution on the latex, as this ensures throughout the web, especially when the web is a complet gulation of the latex, attendedy built up to a considerable thickness. In the case the o ing of the fib r wi h r b r n the d 65 of multi-ply webs such as made on cylinder pavelopment of a bonding fiber of rubber between permaking machines, there is the additional probplies. This sort of practice further means that lem of securing adequate ply adhesion so that when subsequent plying of the web is done under therejwill be little tendency for the rubber-imp s u th r is no t nd y r u a d pregnated product to split on the planes of bondlatex B t e edges of the Sheet and 110 70 ing between plies. gum the felts or other instrumentalities of the In accordance with the present invention, I machine. prepare a plied sheet which is properly impreg- Assuming that chrome-tanned leather waste is nated with rubber and whose plies are so tenaused as a raw material, I prefer to procure such ciously bonded together that there are no defiwaste while it is still wet with the chrome tan- :5 nite planes of cleavage therein. In the case of ning liquor. In this condition, the leather waste waterlaid webs made on papermaking machines, may be put into a heater engine and readily disthese results are had by incorporating a rubber integrated in the presence of water into a pulp coagulant in the wet, freshly-formed web and'apamenable to web formation. Along with the plying latex to the web, as by spraying, before leather water, I prefer to use a relatively small so it is built up into a multi-ply structure as on a proportion, say 10%, o ot fiber, so as to ma-ke-up roll and is then dried, or before it is prove the felting action of the leather fiber united with other webs being similarly treated on the papermaking machine. Cellulose fiber, on a multi-cylinder machine. I e. g., cotton rag fiber, promotes good felting ac- While the process of the present invention is tion, but I have found that natural silk fiber s5 applicable when'cellulosic and/or other kinds of does the same and additionally enhances the fiber are being formed into a web on papermakstrength, pliancy, and smoothness of surface ing or other machinery, it is especially useful in the ultimate product. Accordingly, I prefer to when waste leather stock, e. g., waste leather of use as the fibrous material promoting felting chrome or other tannage, is to serve as raw maaction of the beaten leather stock a low grade terial for making'a leather substitute. Such waste natural silk such as is available at a cost leather stock can be beaten in water to form a not exceeding that of rag stock, wood pulp, or pulp, but the pulp thus produced is of such a similar cellulosic fiber.

slow or slimy'nature that the desired dewater- The wet, freshly-formed web of pulp receives,

40 ing on the papermaking machine, coupled with a' in accordance with my preferred procedure, first running of the machine at an acceptable rate of a spray of coagulant solution, "then a spray of speed, can be had only with a comparatively thin latex, and finally another spray of coagulant web. Consequently, in order to re lize a web solution, before'it is plied into a sheet of the of the desired thickness, such bea en leather desired thickness. The coagulant solution may,

I 45 stock is generally formed into a multi-ply sheet for instance, be one of alum of about 10% from a single web built up on a so-called makestrength. The latex can be sprayed onto the web up roll or from a number of webs plied on a mulat various solids contents, but, considering the ti-cylinder machine. It isthus seen that my inparticular results which I am seeking, it is prefvention fits nicely into the picture when leather erable to work with latex of a solids content,

50 stock is being formed as .ordinarily into a plied including compounding agents, of about 15% to sheet, as I can add the coagulant and latex to 30%. p The latex may, for example, be properly the web while it is pursuing its course as usual compounded with sulphur, zinc oxide, an accelthrough the machine. erator of vulcanization, and suitable pigments While the rubber coagulant may be incorporator dyes, all colloidally suspended in the latex, so

5 ed into the beaten leather stock before it is that there will be no trouble in the spraying operation. The compounded latex may be prepared by adding to latex of about 30% solids content about 3% to 8% sulphur, about 5% to 7% zinc oxide, about 4% piperidine or other accelerator of vulcanization, and'a suitable dye or pigment, e. g., analine black, yellow, or green. These proportions of compounding agents are all based on the weight of the solids content of the latex. The compounded latex may be passed through a homogenizer or colloid mill, to ensure a condition therein compatible with its being properly ,sprayed. The latex so treated may be diluted,

if desired, with water, to a solids content of about 15% for the spraying operation. By the use of such compounded latex, it is possible to realize a smooth, flexible, vulcanized sheet of the desired color and simulating in its strength, tear resistance, toughness, feel, and other qualities a natural leather. The sheet thus produced may be embossed and subjected to other customary leather-finishing operations. The finished sheet can, like natural leather, go into furniture upholstering, automobile tops, book covers, pocketbooks shoe inner and outer soles, counters and box toes for shoes, and other uses.

On the accompanying drawing,

Figure 1 illustrates diagrammatically and conventionally a cylinder machine equipped for the practice of the. present invention.

Figure 2 is a similar illustration of a multicylinder machine equipped for the same purpose.

As shown in Figure 1, a cylinder mould 10 rotates partially submerged in a pulp suspension kept in the cylinder vat 11. The .pulp may be of the character hereinbefore described or any other kind lending itself to deposition from water as a coherent, felted web. The web of pulp progressively deposited on the periphery of the mould is carried out of the vat and is then picked up by the usual transfer felt 12 making constant contact with the unsubmerged portion of the mould under the action of the roll 13. The felt conveys the wetweb to a make-up roll 14 shown. stationed above a roll 15 constituting the terminal roll for the felt. As the web is being convoluted on the roll 14 to the desired thickness, each ply or convolution receives first a spray of alum solution from a nozzle 16, then a spray of properly compounded latex from a nozzle 17, and finally aspray of alum solution from a nozzle 18. Each spray should be delivered over the full width of the web and is preferably kept within a chamber defined by the roll 14 and a box 19 whose inner edges clear the roll sufficiently to permit the web to be built up to the desired thickness.

Inasmuch as the latex is completely coagulated on each of the plies, there is no tendency to squeeze latex from the web in the nip of the rolls 14 and 15 so as to gum the felt. Aside from the fact that the fibers of each of the plies are treated with rubber, the freshly coagulated rubber film developed between the plies ensures tenacious ply adhesion. After the desired sheet thickness has been reached on the make-up roll, the sheet is cut axially of the roll and removed in fiat condition from the roll as ordinarily. The fiat sheet is then dried at elevated temperature for the purpose of causing vulcanization of the rubber binder therein.

When a multi-cylinder machine such as depicted in Figure 2 is employed in making the plied one cylinder mould .and then acquires anotherfrom the next cylinder mould directly on the web previously picked up. Each ply receives the suecessive sprays of alum solution, latex, and alum solution while carried by the felt, before the next ply is deposited thereon. For this purpose, I have shown a series of three sprays 24 located under the felt 20 and inback of each cylinder mould, so that each ply becomes properly treated with rubber before the next ply is superposed thereon. The multi-ply sheet may be taken from the terminal roll 25 for the felt 20 and delivered over a bank of heated drier drums 26, which conduce to vulcanization of the rubber in the sheet, as well as drying of the sheet. a

An important feature of the process of my invention is that a comparatively small amount of rubber need be used in producing a finished article of extraordinary toughness andstrength. In-.

deed, I have found that the incorporation, through my process, of only about 15% to 50% of latex solids into a sheet composed essentially of chrome-tanned leather fibers and built up of plies to a thickness of 70/1000 of an inch makes for a product of such strength and toughness that its tearing cannot be initiated with ones hands.

It is, of course, possible to use artificial aqueous rubber dispersions of the nature of latex, rather than natural latex, as the coagulable binding agent. If desired, a prevulcanized latex such as is sold on the market as Vultex, may be used, in=which case mere drying of the latex even under room temperature conditions yields a vulcanized rubber. Accordingly, the term latex is used in the specification and claims in its comprehensive sense to mean not only natural latex, but also synthetic or artificial latices partaking of the qualities of natural latex. So, too, various wellknown acid solutions or acid salt solutions may be used in lieu of the alum solution as the coagulant for the latex. The strength of coagulant solution may be varied, but in any event, it is desirable to use a solution of such strength as will cause quick and complete coagulation of the latex spray as it strikes the freshly-formed web wet of tanning agent serves as raw'material, this insufficiency may be made up by adding more chromium tanning agent, tannic acid, or the like.

So, too, one may use along with the leather stock 3 various proportions of cellulosic, silk, or other fibers to improve the texture of the web formed on the paper-making machine, as well as to lend 1 other desirable characteristics to the ultimate article. By controlling the beater furnish through the use of the appropriate fibers or mixtures of fibers, as well as tanning or other modifying agents, I can realize in my finished article the qualities of flexibility, softness, or stiffness, as

desired. For instance, so-called fat liquors containing sulphonated castor oil, cod liver oil, or other softening agents for the leather fibers may be added to the furnish for the purpose of lending pliancy and mellowness to the finished articles.

The principles of the present invention extend to the manufacture of a plied sheet from webs of cotton and/or wool or the like formed in a dry way as on carding machines. A web or felt produced in this way may be treated with coagulant solution and latex as it is being wound on a mandrel or take-off roll to the desired thickness. The felt plied sheet removed from the mandrel may be dried and its rubber content vulcanized, if desired. Such an adaptation of my method may be of value especially in those instances when a thick artificial leather, say one whose thickness is A to is desired for such uses as shoe outer soles.

The artificial leather fabricated in accordance with my invention is characterized by having its rubber content distributed therethrough in such a way that, not only does each ofthe plies contain. rubber latex coagulated on its fibers and penetrating thereinto, but the latex coagulated as a film between the plies serves to integrate them most effectively, especially since this film is substantially continuous with the latex coagulated in the plies themselves.

What I claim is: 4

1. As an article of manufacture, a multi-ply sheet of fibers containing rubber latex coagulated not only in its plies but also in between its individual plies as a film serving to integrate the plies, said film being substantially continuous with the latex coagulated in the plies.

2. As an article of manufacture, a multi-ply waterlaid sheet of essentially leather fibers con-' taining rubber latex coagulated not only in its plies but also in between its individual plies as a film serving to integrate the plies, said film bein substantially continuous with the latex coagulated in the plies.

3. As an article of manufacture, a multi-ply waterlaid sheet of essentially chrome-tanned leather fibers containing rubber latex in coagulated and vulcanized condition not only in its plies but also in between its individual plies as a film serving to integrate the plies, said film being substantially continuous with the latex coagulated in the plies.

4. As an article of manufacture, a multi-ply waterlaid sheet of leather fibers and a. smaller proportion of other fibers containing rubber latex coagulated not only in its plies but also in between its individual plies as a film serving to integrate the plies, tially continuous with the plies.

5. As an article of manufacture, a multi-ply waterlaid sheet of leather fibers and a smaller proportion of cellulosic fibers containing rubber latex coagulated not only in its plies but also in between its individual plies as a film serving to integrate the plies, said film being substantially continuous with the latex coagulated in the plies.

6. As an article of manufacture, a multi-ply the latex coagulated in said film being substanwaterlaid sheet of leather fibers and a smaller proportion of natural silk fibers containing rubber latex coagulated not only in its plies but also in between its individual plies as a film serving to integrate the plies, said film being substantially continuous with the latex coagulated in the plies.

'7. A process which comprises treating a web of fibers containing a rubber coagulant with latex, plying the resulting web containing freshly coagulated rubber into a sheet of the desired thickness, and drying the plied sheet.

3. A process which comprises treating a web of waterlaid fibers containing a rubber coagulant with latex, plying the resulting web containing freshly coagulated rubber into a sheet of the desired thickness, and drying the plied sheet at elevated temperature to cause vulcanization of the rubber therein.

9. A process which comprises spraying an aqueous solution of a rubber coagulant onto a wet, freshly-formed web of waterlaid fibers, spraying latex onto the web, plying the resulting web containing freshly coagulated rubber with similarly treated web into a sheet of the desired thickness, and drying the plied sheet.

10. A process which comprises the following progressive steps, viz., depositing fibers from aqueous suspension into a web, spraying an aqueous solution of rubber coagulant onto the wet, freshly-formed web, spraying latex onto the web, again spraying an aqueous solution'of rubber coagulant onto the web, and plying the resulting web containing, freshly coagulated rubher with similarly treated web into a sheet 'of the desired thickness.

ll. A process which comprises the following progressive steps, viz., depositing fibers from aqueous suspension into a web, spraying an aqueous solution of rubber coagulant onto the wet, freshly-formed web, spraying latex onto the web, again spraying an aqueous solution of rubber coagulant onto the web, plying the resulting web containing freshly coagulated rubber with similarly treated web into-a sheet of the desired 20 thickness, and treating the plied sheet at elevated temperature to cause vulcanization of the rubber therein 12. A process which comprises beating stock consisting essentially of waste leather in the 5 presence of water until it has been reduced to a pulp, forming the pulp into a web, spraying latex onto the wet, freshly-formed web, plying the resulting web containing freshly'coagulated rubber with similarly treated, web into a sheet of the 13 desired thickness, and drying the plied sheet.

13. A process which comprises beating stock consisting essentially of chrome-tanned leather waste while it is still wet with tanning liquor in the presence of water until it has been reduced 5 to a pulp, forming the pulp into a web, spraying the web in wet, freshly-formed condition with latex and coagulant solution, plying the resulting web containing freshly coagulated rubber with similarly treated web into a sheet of the 140 desired thickness, and drying the plied sheet.

FRANK O. WOODRUFF. 

